As mobile device technology continues to develop and demand therefor continues to increase, demand for secondary batteries as energy sources is rapidly increasing. Among these secondary batteries, much research has focused on lithium secondary batteries having high energy density and discharge voltage. Such batteries are commercially available and widely used.
Generally, as cathode active materials for lithium secondary batteries, lithium-containing cobalt oxides such as LiCoO2 are mainly used. In addition thereto, use of lithium-containing manganese oxides such as LiMnO2 having a layered crystal structure, LiMn2O4 having a spinel crystal structure, and the like and lithium-containing nickel oxides such as LiNiO2 is also under consideration.
Among cathode active materials, LiCoO2 is widely used due to excellent overall physical properties such as excellent cycle properties, and the like. However, LiCoO2 is low in safety and expensive due to resource limitations of cobalt as a raw material. Lithium nickel based oxides such as LiNiO2 are cheaper than LiCoO2 and exhibit high discharge capacity when charged to a voltage of 4.25 V. However, the lithium nickel based oxides have problems such as high production costs, swelling due to gas generation in batteries, low chemical stability, high pH and the like.
In addition, lithium manganese oxides, such as LiMnO2, LiMn2O4, and the like, are advantageous in that they contain Mn, which is an abundant and environmentally friendly raw material, and thus are drawing much attention as a cathode active material that can replace LiCoO2. In particular, among the lithium manganese oxides, LiMn2O4 has advantages such as a relatively cheap price, high output and the like. On the other hand, LiMn2O4 has lower energy density, when compared with LiCoO2 and three component-based active materials.
To overcome these drawbacks, a variety of materials have been developed. Especially, layered structure transition metal oxides such as LiNi1/3Mn1/3Co1/3O2, LiNi0.5Mn0.3Co0.2O2 and the like including two or more materials of Ni, Mn and Co have been highlighted.
However, these materials do not satisfy requirements of medium and large batteries such as those used in electric vehicles, systems for storing power and the like.
Accordingly, study into Mn-enriched (1−x)LiMO2-xLi2MO3 based materials stable under high voltage is being conducted. However, the Mn-enriched (1−x)LiMO2-xLi2MO3 based materials include a large amount of Mn and thereby are easily oxidized by dissolved oxygen inside an aqueous transition metal solution during synthesis of a transition metal precursor through a co-precipitation method, and, accordingly, synthesis is not easy.
To compensate for this problem, methods such as surface treatment, formation of a core-shell structure and substitution with hetero elements and the like have been tried. However, the methods also are not suitable for easy synthesis. In addition, there are still problems such as additional costs during processes, deterioration of precursor tap density and the like.
As described above, a precursor for preparation of a lithium composite transition metal oxide having satisfactory performance and a lithium composite transition metal oxide obtained from the same has yet to be developed.